Interpretive Summary: One of the applications of plant biotechnology to crop improvement is the use of marker-assist selection (MAS) to transfer of useful traits rapidly and efficiently into breeding lines. MAS has been practiced for major crop plants in both public and private breeding programs and numerous positive results have been published. This paper describes an experiment of applying the target region amplification polymorphism (TRAP) marker technique and MAS to select maintainer lines of confection sunflower. The DNA marker associated with the fertility restorer (Rf1) gene was amplified by a primer designed from a sunflower EST sequence showing homology to the petunia fertility restorer gene in the public database. Our results suggested that MAS can substantially increase the chance of recovering individuals with the desirable genotype from a segregating population.

Technical Abstract:
This preliminary report describes the application of target region amplification polymorphism (TRAP) markers to marker-assisted selection (MAS) in sunflower. TRAP is a fairly new marker technique that takes the advantage of the existing DNA sequence information to generate polymorphic markers near the gene of interest. The objective of this project was to identify maintainer lines from a segregating population. The TRAP marker, a 162-basepair fragment, used in the experiment was amplified by a fixed primer designed against a sunflower expressed sequence tag (EST) that shows homology to the Petunia fertility restorer gene. Two to nine seedlings from each of the 141 F3 families were genotyped with the TRAP marker. Forty families were identified as potential maintainer lines and used as male parents in making test crosses with a confection male sterile line; the progeny were grown in the field to observe male fertility. Only 18 of the 40 selected F3 families were of true rf1/rf1 genotype and can be used as maintainer lines. Although the frequency of recovery of the desirable genotype was 45%, it was significantly higher than that expected from a random sample for a monogenic trait where the homozygous genotype frequency is 25%. This experiment suggested that MAS can substantially increase the chance of recovering individuals with the desirable genotype from a segregating population. Using a marker tightly linked to the target gene and genotyping enough individuals per family are essential to ensure a successful MAS experiment.